Collaborative Research: Dynamic and Thermodynamic Control of Tropical Cyclone Intensity in Sheared Environments

在这项合作研究工作中，主要研究人员将对热带气旋与它们所嵌入的剪切流之间的相互作用的物理学进行全面调查，重点是动力学和热力学过程的相互作用。 他们假设热带气旋是通过涡旋和环境切变流之间的相互作用激发的涡旋Rossby波将低熵中层空气注入涡旋核心而减弱的。 研究重点（动力学和化学过程的相互重要性）偏离了大多数以前的调查，几乎完全集中在直接的动力学效应。 这项研究的出发点是过去十年来两项主要的理论发展：飓风强度热力学控制的定量理论，以及涡旋Rossby波的产生、行为和波/平均流相互作用的理论。 从这些观点出发，主要研究人员将开发一种扩展理论，用于生成和维持涡旋Rossby波，作为涡旋和环境剪切流之间相互作用的结果，并解决这些波通量被动示踪剂进出涡核区域的速率。 这一理论将被用来作为指导，在修改热力学循环，占干空气喷射在中层涡Rossby波。 在开发了这个理论框架之后，主要研究人员将使用一套模型对其进行测试，重点是使用非流体静力学模型以高分辨率进行全三维模拟。 预计该理论将根据这些试验的结果进行修改。 最后，研究人员将利用这一理论来开发一个参数化的罗斯贝波引起的低熵空气通量，用于轴对称模式，包括上述业务预报模式。该项目的智力价值：热带气旋和环境风场之间的相互作用的性质多年来一直是个谜。 以前的努力，以了解和量化这种相互作用几乎完全集中在动态。 在这个项目中，研究人员将结合热力学和动力学方面的相互作用，创造一个一般和完整的描述的过程。该项目的更广泛的影响：飓风强度预报的技能仍然很差，尽管在风暴路径预报的技能有很大的进步。 对热带气旋强度的研究是美国天气研究计划的一个高度优先事项。 这项研究很可能导致对环境切变对飓风强度影响的深入了解;这种深入了解将直接纳入现有的飓风强度预测模型，从而在本奖项的时间范围内直接改善飓风强度预测。 在开展这项研究的过程中，主要调查员将培训飓风科学和飓风预测方面的高级研究生，从而帮助培养新一代的研究人员和预报员。

In this collaborative research effort, the Principal Investigators will undertake a comprehensive investigation of the physics of the interaction between tropical cyclones and sheared flow in which they are embedded, focusing on the mutual operation of dynamic and thermodynamic processes. They hypothesize that tropical cyclones are weakened by the injection of low-entropy, middle level air into the vortex core by vortex Rossby waves excited by the interaction between the vortex and environmental shear flow. The research emphasis (mutual importance of dynamical and thermodynamical processes) departs from most previous investigations, which have focused almost exclusively on direct dynamical effects. The research will have a direct path to improved prediction of tropical cyclones through the improvement of an operational forecast model.The starting point of the research is two key theoretical developments that have matured over the previous decade: the quantitative theory of thermodynamic control of hurricane intensity, and the theory governing the generation, behavior and wave/mean flow interaction of vortex Rossby waves. From these points, the Principal Investigators will develop an extended theory for the generation and maintenance of vortex Rossby waves as a consequence of the interaction between vortices and ambient shear flow, addressing as well the rate at which these waves flux passive tracers in and out of the vortex core region. This theory will be used as guidance in modifying the thermodynamic cycle to account for dry air injection at middle levels by vortex Rossby waves. Having developed this theoretical framework, the Principal Investigators will test it using a suite of models, focusing on fully three dimensional simulations at high resolution using a nonhydrostatic model. It is expected that the theory will be modified based on the results of these tests. Finally, the researchers will use this theory to develop a parameterization of Rossby wave-induced fluxes of low entropy air, for use in axisymmetric models, including the aforementioned operational forecast model.The intellectual merit of the project: The nature of the interactions between tropical cyclones and the ambient wind field has remained enigmatic for many years. Previous efforts to understand and quantify this interaction have focused almost exclusively on the dynamics. In this project, the researchers will marry thermodynamic and dynamic aspects of the interaction to create a general and complete description of the process.The broader impacts of the project: The skill of hurricane intensity forecasts remains poor in spite of substantial advances in the skill of storm track forecasts. Research on tropical cyclone intensity is a high priority under the U.S. Weather Research Program. This research may well lead to an advanced understanding of the effect of environmental shear on hurricane intensity; such advanced understanding will be directly incorporated into an existing hurricane intensity prediction model, thereby leading directly, and within the time frame of this award, to improved hurricane intensity forecasts. In the process of carrying out this research, the Principal Investigators will train advanced graduate students in the science of hurricanes and hurricane prediction, thereby helping to foster a new generation of researchers and forecasters.